Network resource reallocation in iub

ABSTRACT

A method of assigning resources within a network element within which a traffic termination point or AAL 2  termination point has been established. The network element accepts a connection request, and it is then ascertained whether available resources have sufficient capacity to establish the requested connection. In the event that there is sufficient capacity, it is ascertained whether the termination points defined in relation to the available resources fragments the resources such that the connection cannt be established. If the resources are so fragmented, then one or more of the termination points are reallocated, without breaking the connection to which they relate, thereby defragmenting the resources sufficiently that the requested conenction can be established.

FIELD OF INVENTION

[0001] The present invention relates to communications protocols, and,more particularly, to Asynchronous Transfer Modes (ATM) defined inspecifications associated with UTRAN (UMTS Terrestrial Radio AccessNetwork standards defined by the 3 ^(rd) Generation Partnership Project(3GPP).

[0002] The invention has been developed to provide an additional featureto the presently accepted and proposed specifications defined by 3GPP,and will be described herein with reference to those specifications.However, it will be appreciated that telecommunications is a rapidlydeveloping field, and that the invention may well have application tonew and different standards and specifications that evolve from thevarious standards presently accepted or being proposed. Accordingly, theinvention should not be seen as limited to existing specifications.

BACKGROUND TO THE INVENTION

[0003] Various uses of ATM are defined in specifications issued by 3GPP.Of particular relevance is 3GPP TS 25.433 V3.3.0, the contents of whichare incorporpated herein by cross-reference.

[0004] ATM is a connection-oriented technique, comprising theconcatenation of ATM layer links required to effect end-to-end transfersbetween access points. Connection identifiers are assigned to each linkof a connection as required and released when no longer needed. Ingeneral, signalling and user information are carried on separate ATMconnections. In the ATM modes, data to be transmitted is organised intocells.

[0005] At a given interface, in a given direction, the different VirtualPath (VP) links multiplexed at the ATM layer into the same physicallayer connection are distinguished by a VPI. The different VirtualChannel (VC) links in a Virtual Path Connection (VPC) are distinguishedby a VCI.

[0006] The AAL (ATM adaptation layer) performs functions required by theuser, control and management planes and supports mapping between the ATMlayer and the next higher layer. The functions performed in the AALdepend upon the higher layer requirements.

[0007] The AAL uses the ATM layer service and includes multipleprotocols to fit the need of different AAL service users:

[0008] AAL1 supports constant bit rate (CBR), connection-oriented,time-dependent data traffic (circuit, video signal and voice- bandsignal transport);

[0009] AAL2 is an ATM adaptation layer that supports variable bit rate(VBR), connection-oriented, time-dependent data traffic. AAL2 supportspacketised voice and VBR video transmission;

[0010] AAL3/4 supplies sequencing and error detection support tovariable bit rate (VBR), time-independent data traffic. Traffic can beboth connection-oriented and connectionless (computer and network datatransport, for example Frame Relay and SMDS); and

[0011] AAL5 supports variable bit rate (VBR), connection-oriented,time-independent data traffic (AAL5 does not support multiplexing,sequencing or error detection).

[0012] Termination points are managed objects that terminate entities,such as trails and connections. Technology-specific termination pointsare derived using subclassing. In ATM switching a termination point canbe at the virtual path or virtual channel level, and it can be externalor internal.

[0013] In the presently proposed UTRAN specification, a traffictermination point is determined either when a radio link is set up for adedicated channel or a common transport channel is set up for a commonchannel. Each radio link has a traffic termination point, and eachtransport channel within each radio link may have its own AAL2termination point. Similarly, each common transport channel has its ownAAL2 termination point. Once a traffic termination or AAL2 terminationpoint is defined, it is fixed for the duration of the connection.

[0014] In a Node B element, this fixing of termination points cangenerate a resource fragmentation problem. This means that even though aparticular Node B element can have theoretically sufficient capacity toaccept a requested high bandwidth call (such as a video call), but willneed to reject the call because the available resources are scattered.

SUMMARY OF INVENTION

[0015] In accordance with a first aspect of the invention, there isprovided a method of assigning resources within a network element withinwhich a traffic termination point or AAL2 termination point has beenestablished, the method including the steps of:

[0016] accepting a connection request via the network element;

[0017] ascertaining whether available resources have sufficient capacityto establish the requested connection;

[0018] in the event that there is sufficient capacity, ascertainingwhether the termination points defined in relation to the availableresources fragments the resources such that the connection cannot beestablished;

[0019] in the event that the resources are so fragmented, reallocatingone or more of the termination points, without breaking the connectionto which they relate, thereby defragmenting the resources sufficientlythat the requested connection can be established.

[0020] In accordance with a second aspect of the invention, there isprovided a network element having resources to be allocated, withinwhich a traffic termination point or AAL2 termination point has beenestablished, the network element being configured to:

[0021] accept a connection request;

[0022] ascertain whether the available resources have sufficientcapacity to establish the requested connection;

[0023] in the event that there is sufficient capacity, ascertain whetherthe termination points defined in relation to the available resourcesfragments the resources such that the connection cannot be established;

[0024] in the event that the resources are so fragmented, reallocate oneor more of the termination points, without breaking the connection towhich they relate, thereby defragmenting the resources sufficiently thatthe requested connection can be established.

[0025] Preferably, prior to reallocating the termination points, it isdetermined which of the existing termination points should bereallocated to minimize fragmentation of resources within the networkelement, the termination points then being changed in accordance withthat determination.

[0026] Preferably, reallocating the one or more termination pointsincludes:

[0027] sending a Termination Point Switching Request (TPSR) message to aRadio Network Controller (RNC), the TPSR message including portinformation related to the termination points to be switched;

[0028] receiving from the RNC a Switching Request Commit (SRC) message,the SRC message including confirmation that the resource reallocation isto take place, and timing information for synchronization of theresource reallocation.

[0029] In a preferred embodiment, the TPSR includes one or more of thefollowing:

[0030] a Binding ID;

[0031] a Transport Layer & Node B Communication Context ID; and

[0032] a Communication Control Port ID.

[0033] Preferably, the network element is a Node B element in accordancewith a 3GPP UTRA specification.

BRIEF DESCRIPTION OF DRAWINGS

[0034] A preferred embodiment of the invention will now be described, byway of example only, with reference to the accompanying drawings, inwhich:

[0035]FIG. 1 is a flowchart showing the steps involved in a method ofassigning resources within a network element within which a traffictermination point or AAL2 termination point has been established, inaccordance with the invention; and

[0036]FIG. 2 is a schematic of UMTS architecture to which the inventionhas been applied.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

[0037] In its preferred form, the invention is applied to a Node Bnetwork element, forming part of an UTRA-based radio communicationsnetwork for mobile telephony and other types of data transfer, operativeportions of which are shown in FIG. 2. A Core Network (CN) is connectedto the UTRAN by an Iu interface. In the UTRAN, the Iu interface ends atthe Radio Network Controller (RNC). RNCs are connected to each other byan Iur interface.

[0038]FIG. 2 shows two types of RNC: a Serving RNC (SRNC) and a DriftRNC (DRNC). The User Equipment is connected to the Node B by the airinterface Uu and the Node B is connected to the RNC by Iub interface.All the interfaces are well specified to make the network work properly.The Iub interface is specified to use ATM and AAL2 transport mechanisms.

[0039] The operation of the network shown in FIG. 1, in the context ofthe preferred embodiment, will now be described in relation to FIG. 1,in which the Node B network element (ie, a base station) receives arequest for an AAL2 terminated connection. An AAL2 termination supportsvariable bit rate (VBR), connection-oriented, time-dependent datatraffic. Typical examples of the types of data for which suchconnections would be used are packetised voice and VBR videotransmission.

[0040] Upon receiving the request, the Node B ascertains whether thetotal network resources available at that point have sufficientbandwidth to carry the peak expected bandwidth for the data type thesubject of the request. If sufficient bandwidth is available, and theway in which the termination points are allocated allows it, then thenetwork resources sufficient for the requested connection are madeavailable, and the connection established.

[0041] If, on the other hand, there are not sufficient resourcesavailable, the connection request is refused in the usual way. In priorart cases, the connection would also be refused in the event that therewere sufficient resources, but the arrangement of terminations was suchthat the resources were too fragmented to be used by the requested(usually relatively high bandwidth) connection.

[0042] In the present case, if there is sufficient total bandwidthavailable, but previous allocations of available resources havefragmented the resources, the Node B ascertains how to best reallocatethe resources to allow the new connection to be made. Depending upon thecircumstances and implementation, for example, it may be preferablesimply to defragment the resources only to the extent necessary toenable the presently requested connection to be made. Alternatively, agreater amount of defragmentation, ranging from slightly more than theminimum required up to complete defragmentation, may be undertaken. Thiscould mean less of a delay in setting up new connections (subsequent tothat presently requested) that might also not have been fulfilledwithout further defragmentation.

[0043] Once the desired reallocation of resources has been ascertainedin the Node B network element, the element sends a Termination PointSwitching Request (TPSR) message to Radio Network Controller (RNC). TheTPSR message includes port information related to the specifictermination points that the Node B has decided need to be reallocated.In the preferred form, the TPSR will include one or more of a BindingID, a Transport Layer & Node B Communication Context ID, and aCommunication Control Port ID. The actual combination of features will,however, vary between specific embodiments and applications.

[0044] The RNC will usually reply with a Switching Request Commit (SRC)message, which confirms that the resource reallocation is to take place.The SRC message also provides timing information enabling the Node B tosynchronize the resource reallocation, such that the connectionsaffected by the resource reallocations are maintained. The connection isthen established in accordance with the timing information, ensuringthat the reallocation is seamless to users of the system.

[0045] It will be appreciated that the invention can be applied to bothtraffic termination points and AAL2 termination points within a networkelement. In either case, the resource reallocation effectively resultsin switching of communication ports within the Node B network element.

[0046] Whilst the invention has been described with reference to aspecific embodiment, it will be appreciated that the invention can beembodied in many other forms.

1. A method of assigning resources within a network element within whicha traffic termination point or AAL2 termination point has beenestablished, the method including the steps of: accepting a connectionrequest via the network element; ascertaining whether availableresources have sufficient capacity to establish the requestedconnection; in the event that there is sufficient capacity, ascertainingwhether the termination points defined in relation to the availableresources fragments the resources such that the connection cannot beestablished; in the event that the resources are so fragmented,reallocating one or more of the termination points, without breaking theconnection to which they relate, thereby defragmenting the resourcessufficiently that the requested connection can be established.
 2. Amethod according to claim 1, further including the step, prior toreallocating the termination points, of ascertaining which of theexisting termination points should be reallocated to minimizefragmentation of resources within the network element, the terminationpoints then being changed in accordance with that determination.
 3. Amethod according to claim 1 or 2, wherein the step of reallocating theone or more termination points includes the steps of: sending aTermination Point Switching Request (TPSR) message to Radio NetworkController (RNC), the TPSR message including port information related tothe termination points to be switched; receiving from the RNC aSwitching Request Commit (SRC) message, the SRC message includingconfirmation that the resource reallocation is to take place, and timinginformation for synchronization of the resource reallocation.
 4. Amethod according to claim 3, wherein the TPSR includes one or more ofthe following: a Binding ID; a Transport Layer & Node B CommunicationContext ID; and a Communication Control Port ID.
 5. A method accordingto any one of the preceding claims, wherein the network element is aNode B element in accordance with a 3GPP UTRA specification.
 6. Anetwork element having resources to be allocated, within which a traffictermination point or AAL2 termination point has been established, thenetwork element being configured to: accept a connection request;ascertain whether the available resources have sufficient capacity toestablish the requested connection; in the event that there issufficient capacity, ascertain whether the termination points defined inrelation to the available resources fragments the resources such thatthe connection cannot be established; in the event that the resourcesare so fragmented, reallocate one or more of the termination points,without breaking the connection to which they relate, therebydefragmenting the resources sufficiently that the requested connectioncan be established.
 7. A network element according to claim 6,configured to ascertain, prior to reallocating the termination points,which of the existing termination points should be reallocated tominimize fragmentation of resources within the network element, thetermination points then being changed in accordance with thatdetermination.
 8. A network element according to claim 6 or 7,configured to reallocate the one or more termination points by: sendinga Termination Point Switching Request (TPSR) message to Radio NetworkController (RNC), the TPSR message including port information related tothe termination points to be switched; receiving from the RNC aSwitching Request Commit (SRC) message, the SRC message includingconfirmation that the resource reallocation is to take place, and timinginformation for synchronization of the resource reallocation.
 9. Anetwork element according to claim 8, wherein the TPSR includes one ormore of the following: a Binding ID; a Transport Layer & Node BCommunication Context ID; and a Communication Control Port ID.
 10. Anetwork element according to any one of claims 6 to 9, wherein thenetwork element is a Node B element in accordance with a 3GPP UTRAspecification.